Graphene is a single layer of sp2-hybridized carbon atoms that are arranged in two-dimensional hexagonal planes. Because electrons move in graphene as if they have no effective mass, graphene has a very high electron mobility of more than 100,000 cm2/V·s even at room temperature.
Graphene also has a two-dimensional shape, so can be prepared using the CMOS technology currently being used, unlike cylindrical carbon nanotubes. Due to this advantage, graphene is receiving attention as a next-generation semiconductor material which will substitute for a semiconductor device.
However, graphene has a zero band gap, and shows a very high off-current. For this reason, the increase in on-current resulting from the high electron mobility of graphene is set off due to the increase in off-current, and its on/off current ratio have been reported as around 10.
In recent years, to solve this problem of graphene, there have been various attempts such as using nanoribbons, uniaxial strain to graphene, bilayer graphene, and various doping technique to open up the band gap. However, these methods cause additional defects in graphene during processes, thus significantly reducing the electron mobility of the graphene.
Therefore, forming a band gap in graphene compromises the advantage of the high electron mobility of the graphene, thus making it unsuitable to use graphene in a digital device.